Adjusting Filters

Introduction

After exposure values and frames have been found as described in Getting the Right Exposure for Good Point Clouds, it is time to adjust filters. More information about the filters can be found here: Processing Settings.

Reflection filter

The reflection filter removes points that Zivid deem as impacted by reflection and thus erroneous. These are typically seen in the point cloud as “ghost planes” – small regions of points floating mid-air that shouldn’t be there. Note that enabling the reflection filter adds about 10-30 ms of processing time per acquisition.

The following values should be used:

Value	Condition
0	If you know that your scene is not reflective, and you want to optimize acquisition time.
1	Turn on if you have issues detecting parts that are reflective or are inside a reflective bin.

Note

Reflection filter adds up to the following processing time per 3D capture:

	Zivid One+	Zivid Two
Intel UHD750	20 ms	21 ms
NVIDIA 3070	8.5 ms	11 ms

Noise filter

Noise filter removes pixels that have an SNR value below a certain limit. This can be used to remove noisy points (e.g. due to ambient light).

Value	Condition
7	“Almost always”
5-6	It may be necessary to keep the Noise filter value low in order to get points in the following scenes: dark parts strong ambient light large distance

Tip

Noise filter adds negligible processing time.

Gaussian smoothing

The Gaussian smoothing performs averaging on pixels within a small local region. This can be used to suppress sparse noise and align pixels on grid. The higher the threshold, the more aggressive the filtering. The Gaussian smoothing will also correct outliers and can therefore provide a good noise-to-coverage tradeoff.

Value	Condition
<1.0	If you want to preserve as many details and features as possible. Preferred with small objects (sub-cm features).
1.5	For most conditions and medium sized objects.
2.5-5	If you care about smoother and larger surfaces such as flatness of a plane.

Note

Gaussian filter adds up to the following processing time per 3D capture:

	Zivid One+	Zivid Two
Intel UHD750	17 ms	12.5 ms
NVIDIA 3070	2.5 ms	2 ms

Outlier filter

The outlier filter removes pixels that it deems as outliers within a small local region of neighboring pixels. The outliers are measured by how far away they are from their closest neighbors. If the distance exceeds the threshold of the outlier filter, the pixel is identified as an outlier and thus removed from the final point cloud. The unit of the outlier filter threshold is in millimeters, and the smaller the threshold, the more pixels are removed. It is recommended to start with a relaxed outlier filter and then tighten the threshold until you are satisfied with the density/noise level.

Value(mm)	Condition
2-10	Typical for Zivid Two
1-3	Typical for Zivid One+ Small
3-10	Typical for Zivid One+ Medium
10-30	Typical for Zivid One+ Large
50-100	Can be considered if using the camera in one of the following conditions: The image is very defocused (see 2D image in studio) Object is very dark Ambient light is strong relative to projector Scene is far away (>2m)
0	If you have extreme noise, but just want whatever points you can get you may use value 0. This could be in an extremely dark scene, very far away (>2m) or outdoors.

Note

The unit for the outlier filter is in millimeters

Tip

Outlier filter adds negligible processing time.

Contrast Distortion filter

The Contrast Distortion filter corrects and/or removes points that are affected by blurring in the camera lens. In the point cloud, this typically occurs in regions with high contrast (strong specular reflection), and in regions with large texture gradients. The artifact is explained in detail in Contrast Distortion Artifact.

The filter parameter strength states how much a point is corrected in 3D space, and threshold indicates the maximum distance before a point is removed (if removal mode is on). As strength and removal depend on camera focus and orientation (to camera baseline) of the object, its recommended to first tune exposure settings before tuning Contrast Distortion Filter parameters.

Warning

If the strength value is very high, it may overcompensate correction.

Value	Condition
0.1 - 0.2	If you have small contrast distortion effects and no-to-little correction is needed.
0.3 - 0.5	“Almost always”, if your camera has good focus, but contrast distortion is present. Some correction is needed.
0.6 - 0.7	“Common”, if your point cloud is affected by a large contrast distortion. Your camera may be a bit out of focus.
0.8 - 1.0	“Uncommon”, if you have a very high effect of contrast distortion. This often indicates that the camera is out of focus!

Note

Contrast Distortion Correction filter adds up to the following processing time per 3D capture:

	Zivid One+	Zivid Two
Intel UHD750	37 ms	39 ms
NVIDIA 3070	8 ms	9 ms

Contrast Distortion Removal filter adds up to the following processing time per 3D capture:

	Zivid One+	Zivid Two
Intel UHD750	30 ms	32 ms
NVIDIA 3070	5.5 ms	6 ms

Tip

If Contrast Distortion Correction filter is already enabled, then Contrast Distortion Removal adds negligible processing time.

Further reading

Continue to How to Get Good 3D Data on a Pixel of Interest.